Mu Arae
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Mu Arae is a 5th magnitude yellow-orange G-type star similar to our Sun. It lies about 49.8 light years away and is found in the constellation Ara (the Altar), where it is visible with the naked eye. It is estimated to have about 108% of the Sun's mass and may be about 32% larger. It has about 1.7 times the luminosity of the Sun and is suspected to be older, moving into the subgiant phase of its stellar evolution. Mu Arae is metal-rich, even more so than our Sun.
At least three extrasolar planets have been discovered orbiting Mu Arae, including one which scientists believe to be the first rocky extrasolar planet discovered around a main sequence star.
Planetary system
As of August 25, 2004, there were three planets believed to be orbiting Mu Arae. Two are suspected to be gas giants, and one may be a terrestrial planet.
Mu Arae b is one and a half times the size of Jupiter and orbits within the star's habitability zone. Its orbital period is 650 days. This planet's discovery was announced December 12, 2002.
Mu Arae c was announced on June 13, 2002. It is a gas giant three times bigger than Jupiter, and has a highly eccentric orbit that makes its distance from the star differ drastically.
Mu Are d is the least massive extrasolar planet found around a main sequence star. It was discovered on August 25, 2004. Its mass is just 14 times that of Earth. It orbits very close to Mu Arae, completing one revolution every 9.5 days. The discovery was made with the aid of the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph, at the European Southern Observatory's La Silla Observatory in Chile. The data that revealed the presence of this planet was gathered on 8 nights of observations in June 2004.
According to current models of planet formation, ESO scientists believe that Mu Are d is likely to be a rocky planet, not a gas giant; 14 Earth masses is theoretically the maximum size for a terrestrial planet. A rocky planet this size could certainly have formed, since Mu Arae has a higher metallicity than our Sun. If this is the case, Mu Are d may be the first rocky planet discovered outside our Solar System orbiting a main sequence star. The surface of the planet must be very hot because of its closeness to Mu Arae; it is estimated that the surface temperature would be about 900K. Its surface would be volcanic. The probability of life as we know it existing on this planet is thus extremely small.
None of the three planets orbiting Mu Arae are directly visible from Earth using currently available tools. All three were found using the radial velocity method of extrasolar planet detection.
See also
- Extrasolar planet
- List of stars with confirmed extrasolar planets
- PSR 1257+12 - the star with the lightest planets found which are possibly terrestrial.
External links
- Entry at SolStation.com
- ESO Press Release
- Super Earth Space.com
pt:Mu Arae de:My Arae
